1. Field of the Invention
The present invention relates to the use of polyvinyl alcohol-stabilized polymers in mineral building material compositions, more particular in tile adhesives, grouts or spray-applied concrete.
2. Description of the Related Art
Polyvinyl alcohol-stabilized polymers find widespread use in mineral building material compositions, such as coating materials or adhesive-bonding materials, to improve the performance properties of such compositions. The polymers are based in general on ethylenically unsaturated monomers, such as on vinyl esters and ethylene, for example. Mineral building material compositions mixed up with water are required generally to remain stable for a certain time and ought not to exhibit any substantial change in their processing consistency (cement stability or stability of viscosity). Otherwise the user is unable to use the building material compositions to produce constructions having the required performance properties, such as adhesion, imperviosity to water, or mechanical properties, or the user would have to continually produce new building material compositions within short timespans, an unacceptable burden in practice. The use of common polyvinyl alcohols, however, based essentially on vinyl alcohol units and also vinyl ester units and optionally further comonomer units, such as ethylene units, may impact adversely on the processing qualities of polymer-enhanced mineral building material compositions and may lead, for example, to high trowel adhesion or high viscosity. Problems of these kinds occur to an increased extent when mineral building material compositions have relatively high polymer contents. In order to improve the processing properties, EP1984428 advises using protective colloids based on cationic monomers and optionally nonionic comonomers. In practice the cationic monomers frequently contain chloride counterions. When used in mineral building material compositions, however, cationic protective colloid-stabilized systems of these kinds may release odor-intensive substances, which is deprecated, and may also lead to a significant introduction of corrosive substances, such as chlorides. EP0770640 teaches the addition of polymer compositions based on cationic polyelectrolytes and also anonic polyelectrolytes. Such polymers are based on expensive monomers and introduce large amounts of possibly corrosive counterions, such as chlorides, owing to the large number of ionic groups therein. EP0632096 discloses nonionic polyvinyl alcohols which contain units of allylamine, and which when used as a protectine colloid for polymers in mineral building material compositions, accordingly, do not lead to any introduction of corrosive substances, such as chloride. In the context of use in mineral building material compositions, however, there is still potential for improvement in terms of the processing properties, such as the open time, as it is called.
Against this background, the object was that of providing polyvinyl alcohol-stabilized polymers which when used in mineral building material compositions lead to a further improvement in processing properties, such as cement stability and/or stability of viscosity, or else lead, in particular, to a prolongation of the open time, and as far as possible release less odor-intensive substances. The polyvinyl alcohols ought also to be inexpensive and to be obtainable according to establisped processes that are not costly or inconvenient, moreover.